An EMI gasket is a conductive interface material which is used to electrically connect an electrically conductive shield with a corresponding section of an electrical ground, such as a ground trace of a printed circuit board (PCB). Preferably, an EMI gasket should be highly electrically-conductive and conformal. Such a conductive interface material is required when mating surfaces of an electronic apparatus are not exactly conformably dimensioned, such that gaps are formed upon mating engagement of the mating surfaces. These gaps permit undesirable internal and external electromagnetic interference (EMI) which can cause the disruption of the electronic apparatus.
Presently, EMI gaskets are almost exclusively installed directly onto a conductive surface. More particularly, present manufacturing techniques for installing EMI gaskets include the following: dispensing a conductive paste or a conductive liquid material directly onto a conductive surface and curing the dispensed material in-situ; die-cutting a conductive sheet material having an adhesive backer and then transferring, positioning and adhering the dimensioned material directly to a conductive surface; or mechanically fastening a conductive material to a conductive surface.
Although the aforementioned manufacturing and installation techniques are effective in certain instances, shortcomings associated with these manufacturing and installation techniques include: complicated, cumbersome, labor-intensive and expensive automation equipment; and ineffective adhesion to certain conductive surfaces. Additionally, logistic complications may be caused by multiple or even duplicative shipments of parts and materials for processing among a diverse group of vendors.
While discrete, additional EMI gasket installation equipment is generally undesirable and labor-intensive, surface-mount technology (SMT) machines are well-known, high-speed machines which are in widespread use in the electronics industry. For example, SMT machines are widely utilized by cellular phone manufacturers to populate printed circuit boards (PCBs).
As is well understood by those skilled in the art, SMT machines utilize a vacuum head on the end of a high-speed gantry system to pick and place tape-and-reel fed PCB components onto surface-mount pads on a PCB. These pads are usually pre-screened with solder-paste and then sent through a solder reflow oven (such as infrared--IR, vapor-phase, or convection) to melt the solder joints, thereby forming an electrical and mechanical connection.
In an effort to eliminate the use of EMI gaskets, SMT-compatible "cans" were developed, which are simply formed or drawn metal shields that can be soldered to a ground trace of a PCB, thereby effectively forming a Faraday Cage. This serves, therefore, to eliminate the gasket from the entire process. Shortcomings associated with the use of soldered cans include: difficulty in the re-work of a soldered can; inspection of components underneath a soldered can be extremely difficult; and when large cans are desired, the non-flatness of the cans prevents proper solder joints from forming.
Alternatively, metal spring-finger contacts may be employed which can be SMT-fed; however, such metal spring-finger contacts provide only discrete grounding points between a shield and PCB ground trace, and thus are ineffective as operating frequencies continue to rise.
The foregoing illustrates limitations known to exist in present EMI gaskets and EMI gasket installation methods. Thus, it is apparent that it would be advantageous to provide an improved EMI gasket directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided, including features more fully disclosed hereinafter.